In 1841 James Clark Ross and crew in two tiny ships “Erebus” and “Terror” discovered Ross Island. They named the highest peaks after their ships and quickly recognized their volcanic origin. Erebus was in a state of vigorous eruptions at the time. Later in the early 1900’s British explorers explored parts of the island and found it was completely volcanic and composed of solidified lavas and associated deposits from explosive eruptions.

Ross Island is now home to the U.S. Antarctic Program’s McMurdo Station, Antarctica’s largest research base. Erebus volcano is the world’s southernmost active volcano and is the 18th largest in the world based on volume. It is both awe-inspiring and threatening to the inhabitants of McMurdo Station (1000 people in the summer and ~180 in the winter) as its summit (12,448 ft elevation/volume 2170 km3) and persistent gas plume dominates their northern skyline (Plate 1).

Although there have now been over 40 years of scientific expeditions to study Erebus volcano, geologic studies of Ross Island’s other volcanic centers ­­– Mt. Terror (3262 m, 1700 km3), Mt. Bird (1800 m, 470 km3) and Hut Point Peninsula (100 km3) ­– are remarkably sparse and outdated. As a consequence, our knowledge of the geological origin of the Ross Island volcanoes is incomplete.

Plate 2: Schematic of plume model for volcanism at Ross Island. The insert shows the radial symmetry of vents at 120 degrees angles surrounding Erebus volcano on Ross Island and also for the older (>5 Ma) Discovery volcanic center, which is south of Ross Island in southern McMurdo Sound.

Using funding from the National Science Foundation (NSF), we are conducting a field and laboratory based study to examine the hypothesis that volcanism on Ross Island is the surface expression of a deep mantle upwelling in the form of a mantle plume or hot-spot (Plate 2). This aspect of our research is timely in that recent “geophysical observations” indicate that the mantle beneath Ross Island is hotter than its surroundings.

Our study will also provide a critical contextual perspective for the well-studied and iconic Erebus volcano. While Erebus is the only currently active volcano on Ross Island, understanding past volcanism on Ross Island’s other volcanoes (Mt. Terror, Mt. Bird and Hut Point Peninsula) is essential to predicting future volcanic activity, both at Erebus volcano and elsewhere on Ross Island. The key to predicting a volcano’s future is understanding its past.

Plate 3: Satellite image of Ross Island showing radial symmetry of Mounts Bird and Terror and Hut Point Peninsula around the dominant and larger Erebus volcano. The sites we propose to sample and visit are indicated. This image shows the extensive area of exposed rocks on the east flank of Mount Terror, most of which has never been sampled or examined. We expect the oldest samples for Mounts Terror and Bird to be exposed in marine cut cliffs around the north coast in Lewis Bay. Sampling of these sites will require fieldwork early in the field season at a time when there is still sea ice available for helicopter landings. Image from Google Earth.

During the field portion of the study (Oct 22-Nov 28, 2012), our team will be collecting about 60 samples from the summits and flanks of Mt. Terror, Mt. Bird and Hut Point Peninsula on Ross Island. This effort will involve using helicopters and snowmobiles to circumnavigate Ross Island to collect lava samples from the sea cliffs along the ice edge, as well as using helicopters to go to the summits of Mt. Terror and Mt. Bird to collect samples from exposed lava flows and vents (see Plate 3). We will also be camping for several days on the flanks of Mt. Erebus on “Fang Ridge” to collect samples from its ancient eruptions and also on the coastline at Cape Bird penguin rookery.

For the laboratory based portion of the study we will be measuring the geochemical properties of the lava samples back in the US at our state-of-the-art laboratories at the University of Wyoming, New Mexico Institute of Mining and Technology, University of Oregon, Arizona State University and Woods Hole Oceanographic Institution. These new data combined with our previous research on the Erebus volcano, will provide essential information on the nature of the mantle source beneath Ross Island and the causes of its volcanism, both past and present.

Team

Ken Sims is an associate professor at the University of Wyoming, the PI on the NSF grant funding this research. This will be Ken’s 10th season in Antarctica (eight as a mountain guide and two as a PI on scientific grants). http://geology.uwyo.edu/kenwwsims

Philip Kyle is a professor at New Mexico Institute of Mining and Technology, co-PI on the NSF grant. This will be Phil’s fortieth season! in Antarctica. http://www.ees.nmt.edu/kyle/

Dan Rasmussen is an MSc student working with Phil Kyle at NMT. He was an undergraduate student at the University of Oregon where he did a senior thesis with Paul Wallace as his adviser. This is Dan’s first season in Antarctica.

Comments

1) “If you are studying the volcanic history of Ross Island why are you not taking samples from Mt. Erebus, the most recently active volcano?”

We are indeed very interested in Erebus volcano. On several of my other expeditions down here, both as a mountaineering guide and as a scientist, I have worked exclusively on Erebus volcano. There are now about 75 scientific publications from studies of Erebus volcano including three of mine (one of which was just published 2 weeks ago:). In contrast, there have been few studies on the other volcanoes of Ross Island and the data are old and sparse/ limited. So we are focusing on these under studied volcanoes and will combine our new data and the understanding we are developing with all the existing Erebus data to better understand the volcanic history of all of Ross Island.

2) What is the asthenosphere? – Now this is a complicated question to answer in a short response, but here I go. The earth is layered and this layering can be considered either from a chemical perspective or a material properties perspective.

From the chemical perspective the earth has a heavy iron core and an outer silicate layer that is divided into an lighter lower density crust and a heavier residual mantle. One way to consider this is-if you take the material that the earth accreted from – meteorites- and put them all in a bucket and heat it up until it melts the metal will sink to the bottom (the core), the scum will float to the top (the crust) and everything else left over will be in the middle (the mantle).

From the mechanical properties perspective the layering is divided according to how rigid or stiff it is. So since I mentioned the core here it is worth noting that our Fe-Ni (and whatever else is in there) is a solid inner core and outer liquid core. This difference is what creates our Earth’s magnetic field as it is a dynamo.

So now to answer your specific question- the upper part of the Earth is divided into the lithosphere or rocky sphere (Litho is Greek for rocky), and asthenosphere or weak sphere (aestheno is Greek for weak). The outer crust with all the tectonic plates moving around is the lithosphere and they are riding on a hot mechanically weak, or ductile layer which is the Earth’s lithosphere.

Finally, the magma is coming out of the aesthenospheric mantle through the crust and then through the ice.

Did I lose you? I hope not. Thanks again for your questions. Send any more you may think of.

All the best,
Ken

Ansel Visser

Laramie, Wyoming

November 1, 2012, 8:12 pm

Hello ken and fellow scientists,

I am very excited to read about your adventure in Antarctica. I have two questions. The first is if you are studying the volcanic history of Ross island why are you not taking samples from Mt. Erebus, the most recently active volcano? The second question is what is the asthenosphere. I can’t tell if the magma is coming out of ice or solid ground.

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